a very-long range supersonic strategic reconnaissance aircraft for the purpose of supporting the V bombers during their offensive mission. As such, the Air Staff set about formulating an Operational Requirement; in 1954, Specification OR.330, which specified the required performance attributes for such an aircraft, was issued accordingly. The envisioned reconnaissance aircraft would be capable of successfully entering the airspace of the Soviet Union while avoiding the sophisticated hostile air defenses intended to combat such an intrusion. In order to achieve this feat, the aircraft would have to be capable of maintaining Mach 2.5 at an altitude of 60,000 ft (18,300 m), along with the ability to attain at least Mach 3 and operate at a maximum range of 5,754 mi (9,260 km). By operating at such a high altitude and speed, along with assorted advanced electronic systems on board, it was believed that the specified aircraft would be capable of evading the threats posed by Soviet interceptor aircraft and newly developed surface-to-air missiles alike. Upon its issuing, Specification OR.330 effectively called for the most ambitious high-performance aircraft in the world. At the time, Britain lacked any operational combat aircraft capable of supersonic flight; as such, meeting the specification required industry to embrace leading edge aerodynamic theory, new materials and futuristic propulsion systems. In response, there were a total three submissions made from British aircraft manufacturers: the Handley Page HP.100, Vickers SP4, and the Avro Type 730. All were futuristic delta or needle shapes in appearance employing multiple engines, 12 on the HP.100, 16 mounted horizontally at the rear of the Vickers. Work on the HP.100 proceeded to a full-scale mockup and large-scale wind tunnel testing. However, in mid-1955, Avro were issued with a contract by the Ministry of Supply to develop their submission aircraft. Development work and repurposing The Avro 730 was an unswept canard design, making extensive use of stainless steel and powered by a total of four Armstrong Siddeley P.176 turbojet engines. As an aid to development, the Bristol Type 188 aircraft was built to test the compound-delta wing shape, and later, the effects of prolonged supersonic flight on metal. Up to 10 prototypes of the aircraft were proposed, necessitated in part by a decision made part-way through the development process to give the aircraft a bombing capability. The initial version of the aircraft had been intended strictly for the aerial reconnaissance role, for which it would have